Recently, due to a rise in the standard of living and various desires of consumers, various kinds of shoes having a variety of designs have been manufactured. Further, various special shoes having various functions have come onto the market.
At first, shoes served as means simply for protecting the feet. However, the shoes have been developed so as to be one device having various functions.
That is, the production of shoes having functions suitable for various purposes, for example, safety shoes for special workers, exercise shoes without heels, and shoes for diabetics, has increased.
Meanwhile, according to oriental medicine, acupuncture points interacting with respective organs of the body are distributed throughout the hands and feet.
It is known that internal organs of the body, connected to the acupuncture points, are treated by applying pressure to or stimulating the acupuncture points connected to the hands and feet.
The method of using the acupuncture points distributed throughout the hands and feet has been widely used as indirect and auxiliary therapy for human bodies.
For example, hand acupuncture and foot acupuncture are representative of the method using the acupuncture points. The hand acupuncture and the foot acupuncture treat the body by stimulating respective acupuncture points of the hands and feet connected to specific organs in the body using a needle.
Further, external stimuli for treating the body include acupressure treatment, moxibustion, low frequency treatment, a magnetic field, and electric stimulus, in addition to acupuncture.
In this case, the acupuncture or the acupressure treatment directly stimulates nerves, thus strengthening the activity of nervimotion. Conversely, the low frequency or the magnetic field penetrates into the body, thus performing a special treatment rather than directly stimulating the nerves.
The treatment using the external stimuli originates from oriental medicine. Currently, a substantial effect of the treatment using the external stimuli is demonstrated, so that the treatment has been used in various fields, both in oriental medicine and in western medicine.
Various physical instruments using the methods are prevalent. The methods are applied to shoes, so that they are widely used.
A representative conventional shoe for putting pressure on the sole is made such that the surface of an inner sole laid in the shoe is irregular. In addition to such a shoe, various kinds of functional shoes have been used.
Further, one example of shoes using electricity or a low frequency as external stimuli which are useful for the body is disclosed in Korean U.M. Publication No. 1986-5561, which deals with a shoe having a discharge electrode device.
According to the prior art, a current generated by pressure acting on a piezoelectric actuator is transmitted through a discharge electrode connected via a lead wire.
In this case, the current generated by the piezoelectric actuator is transmitted through the sole. However, the prior art is problematic in that little electricity is applied.
That is, the piezoelectric actuator serves as a storage battery which has a voltage varying with external force. Conversely, when electricity is supplied from the exterior, the pressure of the piezoelectric actuator varies.
The former case is applied to an igniter of a gas range, which uses a variation in pressure. The latter case is applied to electronic equipment, such as an accelerometer, using the variation in pressure.
The aforementioned prior art uses an electric current.
However, the current generated in a conventional piezoelectric sensor is very weak, that is, about several pico-amperes (pA). Meanwhile, the resistance of the sole surface ranges from several hundred ohms (Ω) to several mega-ohms (MΩ). Thus, the prior art is problematic in that little generated micro current is transmitted through the surface of the sole to the interior thereof.
Further, the prior art is problematic in that there is little effect, even though the current is transmitted to the sole.
That is, according to the aforementioned construction, current is conducted through a single discharge electrode, and flows along the shortest distance in view of conduction characteristics. Thus, the current flowing through the single discharge electrode flows along a rectilinear course which is the shortest distance to another discharge electrode. Hence, there is little effect of current acting on the feet.
Due to these problems, the aforementioned construction is impractical, so that it is seldom used.
Further, a shoe having a physical therapy function is disclosed in Korean U.M. Registration No. 20-274120
According to the prior art, a power supply unit is provided in the shoe, so that a low frequency is generated by power supplied from the power supply unit.
However, since the shoe has the following problems, it is useless in actual life.
First, the power supply unit comprises a battery or a structure which must be charged from the outside to supply power.
Such a structure does not consider recovering power when walking, so that much power is consumed. Thereby, a power changing or charging operation is frequently required, thus inconveniencing a user. Hence, it is difficult to use the shoe in actual life.
Second, the shoe comprises a complicated structure having a control part, a low-frequency output part, a low-frequency oscillation part, and others.
A general low-frequency generator is entirely installed in the shoe, so that the space for installing the low-frequency generator in the actual shoe is insufficient. Further, the construction is complicated, so that the shoe may easily malfunction due to external impacts.
Third, the manufacturing cost of the low-frequency generator having the complicated construction is high, thus leading to an increase in the cost of the shoe. Further, the low-frequency generator is heavy, so that the total weight of the shoe is increased.
The heavy shoe goes against the trend towards lighter shoes, so that there is little possibility that the heavy shoe will be used in actual life.
In order to solve the problems, a shoe in which a micro current flows using power generated by applying a force, such as impacts or pressure, to a piezoelectric actuator has been proposed.
For example, according to Korean Patent Appln. No. 10-2005-30874 which was invented by the same inventor, a piezoelectric actuator is provided in a heel portion of the outsole of a shoe. According to the power of the piezoelectric actuator, a micro current is applied to the shoe.
However, the current generated in the conventional piezoelectric sensor is determined depending on the pressure of the sole. A user's weight or an applied impact may be irregular, or pressurization may be slowly performed.
That is, a voltage value and a current value are irregular according to the user's weight or walking manner. In the case where the irregular pressure acts on the piezoelectric actuator, an irregular micro current flows whenever contact occurs.
Meanwhile, the shoe equipped with the low-frequency generator or the shoe applying a micro current using the piezoelectric actuator uses an AC power source. However, a DC power source is mainly used for treatment.
Further, when a user wears the shoe on a rainy day or exercises with the shoe on, he or she wants to stop the flow of the micro current. However, the conventional shoe is problematic in that it is impossible to control the transmission of the micro current as desired.
Further, shoes currently on the market currently have only a simple single function. The shoes do not efficiently demonstrate their functions.
Therefore, if a shoe which has multiple functions and can be used for medical treatment is produced, the shoe is not merely a means for protecting the foot, but can be used as the auxiliary means for several treatments which are useful for the body in daily life.